Creating Symmetric Objects with the Duplicate Tool

Many real world objects are symmetric in some way. For example, left and right sides of a human head are quite similar. The SDS 'Duplicate' tool is provided for utilizing this observation in SDS modeling. You only have to model 50% of the object and use a transformation tool to get the other part modeled.

Load 'tutorprojects/sds/halfhead'

The Duplicate tool takes care of three things. It first duplicates all points, edges and faces in the selected object. Then it finds all open edges in the original and duplicated faces and connects them with an appropriate number of new faces. Finally, the tool selects the duplicated faces so that you can immediately move, mirror, scale or otherwise transform them.

1. Go to the Select Window's geometry tab and click the right mouse button. A pop-up menu is opened. Select Paste from a file option and load the 'tutorprojects/modeling/sds/halfhead' object.

2. Select the loaded face and enter 'Face' mode by selecting the near southeast compass menu.

3. Click the Duplicate tool.

Duplicate tool

Enter face editing mode
Duplicated faces mirrored

Note: Duplicate tool automatically selects the duplicated part of the object. Be careful not to change the selection, because re-selecting the exactly overlapping faces is very difficult. If you accidentally change the selection, undo the 'Duplicate' operation and execute it again.

4. Activate the Mirror tool; it's located in the Transformation tab.

Mirror tool

Then enter two points through the view window to define vertical mirroring axis.

The result is a complete face. The tool connects also the back, top and bottom sides of the face. If this is undesirable, select the connecting faces using the top view and apply the 'Destroy F' tool to them.

A cube

A cube is an object, which clearly has an axis of symmetry: its left and right side faces are identical. So, we only have to create one face and get the other face by using the Duplicate tool. Side faces are created automatically by the tool.

Activate the SDS Rectangle tool...

1. Create a SDS rectangle consisting of 2x2 points.

Enter two points through the view window to create a SDS rectangle

2. Select the rectangle and enter the face editing mode. Now the control bar shows you all the SDS specific tools. Click the Duplicate tool.

This duplicates the single face of the rectangle object and creates four new faces to connect the edges of the original and the new face.

Note: the tool automatically selects the duplicated face.

3. Activate the Transformation/Move tool and enter two points through the view window to displace the duplicated face from its original position.

The duplicated face moved

Extruded mesh

In this example, we create an object used by body builders to train their biceps.

1. Activate the SDS/Rectangle tool. This time set the resolution to 8x4 through the control bar (U=8, V=4).

SDS mesh consisting of 8x4 control points
Extruded mesh

2. Enter Edit/Face mode and click the Duplicate tool. Use the Move tool (or one of the normal handles) to displace the duplicated faces from the original faces.

Bent mesh

3. Switch to the point editing mode. Select both cross-sections next to the ends of the object and move them backward to bend the object as shown below.

A mesh with holes

The Duplicate tool finds all open edges in the surface to be extruded, including 'holes':

1. Create a SDS rectangle consisting of 8 x 8 control points.

2. Enter the face editing mode and delete a couple of faces from the mesh using the 'Destroy F' tool.

Select a couple of faces and destroy them with the Destroy F tool

Destroy Face tool

3. Click the Duplicate tool and use the Move tool to move the duplicated faces apart from the original faces.

A mesh with holes extruded with the Duplicate tool

A coffee cup

In this example, we create a coffee cup by modeling the outer surface for the cup first. The inner surface for the cup is created with the 'Duplicate' tool (the inner surface is otherwise identical to the outer surface but slightly smaller).

1. Take a top view and create a SDS sphere. take a front view and select the faces near the north pole as shown in the image.

Select the topmost faces
Upper faces destroyed

2. Apply the 'Destroy F' tool to the selected faces.

3. Click the 'Duplicate' tool. This creates the inner surface for the cup. Drag one of the scale handles at the end of normal handles to scale the inner faces smaller.

Outer faces duplicated and scaled inwards to form the inner surface for the cup
Select two opposite faces

We could create a handle for the cup as demonstrated in some of the earlier tutorials. However, let's be more creative this time. The cup has a round base, and therefore it is not a practical cup to use. We can duplicate and mirror the cup in vertical direction to create a proper base for it.

4. Select two opposite faces near the bottom of the cup.

5. Click the 'Destroy F' tool to delete the selected faces. This creates two rectangular holes in the outer surface of the cup. Click 'Duplicate' and then use the 'Mirror' transformation tool to flip the duplicated faces under the cup as shown in the image on the right.

A cup base created by mirroring the duplicated faces

Other examples

Duplicate + Scale
Duplicate + Mirror